The Anonymous Widower

Thoughts On A Battery Electric Class 88 Locomotive On TransPennine Routes

In Issue 864 of Rail Magazine, there is an article, which is entitled Johnson Targets A Bi-Mode Future.

As someone, who has examined the mathematics of battery-powered trains for several years, I wonder if the Age of the Hybrid Battery/Electric Locomotive is closer than we think.

A Battery/Electric Class 88 Locomotive

 After reading Dual Mode Delight (RM Issue 863), it would appear that a Class 88 locomotive is a powerful and reliable locomotive.

  • It is a Bo-Bo locomotive with a weight of 86.1 tonnes and an axle load of 21.5 tonnes.
  • It has a rating on electricity of 4,000 kW.
  • It is a genuine 100 mph locomotive when working from 25 KVAC overhead electrification.
  • The locomotive has regenerative braking, when working using electrification.
  • It would appear the weight of the diesel engine is around seven tonnes
  • The closely-related Class 68 locomotive has a 5,600 litre fuel tank and full of diesel would weight nearly five tonnes.

It is worth looking at the kinetic energy of a Class 88 locomotive hauling five forty-three tonne CAF Mark 5A coaches containing a full load of 340 passengers, who each weigh 90 Kg with baggage, bikes and buggies. This gives a total weight would be 331.7 tonnes.

The kinetic energy of the train would be as follows for various speeds.

  • 90 mph – 75 kWh
  • 100 mph – 92 kWh
  • 110 mph – 111 kWh
  • 125 mph – 144 kWh

The increase in energy is because kinetic energy is proportional to the square of the speed.

Supposing the seven tonne diesel engine of the Class 88 locomotive were to be replaced by a battery of a similar total weight.

Traction batteries seem to have an energy/weight ratio of about 0.1kWh/Kg, which is increasing with time, as battery technology improves.

A crude estimate based on this energy/weight ratio would mean that at least a 700 kWh battery could be fitted into a Class 88 train and not make the locomotive any heavier. Given that lots of equipment like the alternator and the fuel tank would not be needed, I suspect that a 1,000 kWh battery could be fitted into a Class 88 locomotive, provided it just wasn’t too big.

A short length of electrification could be installed at terminal stations without electrification to charge the batteries during turnround.

This size of battery would be more than large enough to handle the braking energy of the train from full speed, so would improve the energy efficiency of the train on both electrified and non-electrified lines.

It would also contain more than enough energy to accelerate the train to line speeds that are typical of non-electrified routes.

TransPennine Express will soon run similar rakes of coaches hauled by Class 68 diesel locomotives between Liverpool and Manchester Airport and the North East.

The following sections of the Northern TransPennine route, are not electrified.

  • Stalybridge and Leeds – 35 miles taking 46 minutes
  • Leeds and Colton Junction – 20 miles taking 18 minutes
  • Northallerton and Middlesbrough – 21 miles taking 29 minutes
  • York and Scarborough – 42 miles taking 56 minutes

When running on these sections without electrification, consider the following.

  • The train consists of modern coaches, which must be energy efficient.
  • The train would enter the sections with a full battery, that had been charged using the 25 KVAC electrification on part of the route.
  • Scarborough and possibly Middlesbrough stations, would have means to charge the battery.
  • The train would enter the sections as close to line speed as possible, after accelerating using electrification.
  • Regenerative braking would help conserve energy at any planned or unplanned stops.
  • The driver will be assisted by a modern in-cab signaling and a very capable Driver Assistance System.
  • Stadler and Direct Rail Services must have extensive theoretical and measured data of the performance of Class 88 locomotives and the related Class 68 locomotive, when they are hauling trains across the Pennines, which will enable extensive mathematical models to be built of the route.

For these reasons and especially the last about mathematical modelling, I believe that Stadler could create a battery/electric locomotive based on the Class 88 locomotive, that would be able to bridge the electrification gaps on battery power and haul a five-coach train on the Northern routes across the Pennines.

A Quick Look At The Mathematics

As I said earlier, the weight of a Class 88 locomotive and five Mark 5A coaches, full of passengers is 331.7 tonnes.

There would appear to be little weight difference between a diesel Class 68 locomotive and an electro-diesel Class 88 locomotive, so in this rough exercise, I will assume the train weight is the same.

The current Class 185 trains, that run across the Pennines have the following characteristics.

  • Three-cars
  • A weight of 168.5 tonnes.
  • A passenger capacity of 169.
  • Installed power of 560 kW in each coach, which means there is 1560 kW in total.

If each passengers weighs 90 Kg, with all their extras, a full train will weigh 183.7 tonnes.

So a full train has a power-weight ratio of nine kW/tonne, which must be sufficient to maintain the timetable across the Pennines.

The diesel Class 68 locomotive, which will be hauling trains on the route in the New Year,  has an installed power of 2,800 kW, which gives a power/weight ratio of 8.4 kW/tonne.

I would be interested to know, if a Class 88 locomotive running in diesel mode with a power output of only 700 kW, could take one of the new trains across the Pennines. I suspect Stadler and/or DRS know the answer to this question.

But it would be a power/weight ratio of only 2.1 kW/tonne!

The challenging route is between Stalybridge and Leeds via Huddersfield, where the Pennines has to be crossed. I’m pretty certain, that all the other sections lack the gradients of the section between Stalybridge and Leeds.

So would a Class 88 locomotive with a 1,000 kWh battery be able to cross the Pennines with a full train?

Theoretically, up and down routes are good for battery/electric trains with regenerative braking, as energy used going uphill can be recovered on the other side.

The thirty-five miles between Stalybridge and Leeds take forty-six minutes, so for how long on this journey will the locomotive be applying full power? Perhaps for twenty minutes. If the locomotive applied an average of 2,000 kW for twenty minutes or a third of an hour, that would be 667 kWh.

With an electric multiple unit like an Aventra, where most if not all axles are driven and they can also contribute to regenerative braking, reasonably high rates of braking energy can be recycled.

But what proportion can be recycled, when the locomotive is doing all the regenerative braking. Any braking done by disc brakes on the coaches will result in lost energy.

As an aside, I wouldn’t be surprised to find out that train manufacturers simulate train braking in order to develop braking systems, that turn less energy into wasted heat.

I’d also love to see a simulation using Stadler’s real data of a Class 88 locomotive with batteries attempting to cross the Pennines, with a rake of Mark 5A coaches!

  • What size of battery will be needed?
  • Can this battery be fitted in the locomotive?
  • Would distributing the batteries along the train increase performance?
  • Would short lengths of electrification on the route, increase performance?

I was doing problems of similar complexity to attempt to design efficient chemical plants nearly fifty years ago. We had our successes, but not as great as we hoped. But we certainly eliminated several blind alleys.

My figures don’t show conclusively, that a Class 88 locomotive with a 1,000 kWh battery instead of a diesel engine and all the related gubbings, would be able to perform services across the Pennines.

But.

  • Battery technology is improving at a fast pace.
  • Train manufacturers are finding surprising ways to use batteries to improve performance.
  • I don’t have access to Stadler’s real performance figures of their diesel locomotives.
  • Finding a way to make it work, has a very high cost benefit.

Who knows what will happen?

125 Mph Running

The Class 88 locomotive, has a similar power output to the 125 mph Class 91 locomotive of the InterCity 225 and I believe that the locomotive might have enough power, when running on 25 KVAC overhead wires to be able to haul the train at 125 mph on the East Coast Main Line.

Conclusion

I believe that it is possible to create a battery/electric version of the Class 88 locomotive, that should be able to take a rake of five Mark 5A coaches across the Pennines.

Timings across the Pennines would benefit substantially, without any new infrastructure, other than that already planned and the charging system at Scarborough.

December 8, 2018 - Posted by | Transport | , , , ,

2 Comments »

  1. An aspect that doesn’t seem to have been thought about yet is that if you have a section with very steep gradients with a battery bi-mode locomotive you can just electrify the section with the very steep gradients are. Still much cheaper than electrification of the whole route, and you can actually top the battery up rather than running it down.

    Comment by Hannah Lane | December 10, 2018 | Reply

    • Absolutely! And you can sneak in sections of smart third rail in tunnels and on viaducts! The advantages of third rail, is that it is n’t an eyesore and connects automatically without driver action to the train. For safety reasons, it would only be switched on, when a train is on top. This could be automatic.

      Comment by AnonW | December 10, 2018 | Reply


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